Design Review: November 17,2011

subduedjourneyΛογισμικό & κατασκευή λογ/κού

28 Οκτ 2013 (πριν από 4 χρόνια και 15 μέρες)

85 εμφανίσεις



Design Review: November 17,2011



Team Members: Allan Davis






Carlos Gonzalez






Cooper McBride


Objective


Design, fabricate and test a 900
-
Mhz
directional panel antenna for Schweitzer
Engineering Laboratories

2

Applications


Radios provide comm channels for electric utility
protection, monitoring, and control


Economical alternative to fiber
-
optic cable


Backup primary protection channels

3

Other Uses


Oil and gas pipelines and refineries


Water and wastewater treatment facilities


Fire and security alarm remote monitoring


Many more possible applications of wireless
communications for critical infrastructure

4

What SEL Needs


An antenna that will have performance similar to a 5
-
element Yagi antenna


The antenna will be used with the SEL
-
3031 transceiver


5

Why a Panel Antenna?


SEL is currently selling directional Yagi antennas


An example of a 5
-
element Yagi is shown here

6


This is a panel antenna made by the same company

7


Panel Antenna Pros
:


Lower cost than Yagi


Compact package


Ease of installation


SEL can manufacture a panel antenna using existing
facilities and equipment


Panel Antenna Cons
:


Can’t increase directivity by adding elements as with Yagi


More ways for material inconsistencies to affect
performance


8

Specifications


Directional


Vertical or Horizontal Polarization


Gain:
≥8 dBi


HP Horizontal Beamwidth: 45
°


HP Vertical Beamwidth: 65
°


Operating Frequency Range: 900
-
930 MHz


~ 3% Bandwidth


VSWR:
≤1.5:1


Characteristic Impedance: 50



Designed Using Printed Circuit Board Technology

9

Example Radiation Patterns

10

Dipole

Yagi

Current Design
-

Bowtie


This is a type of planar dipole antenna


θ
0

is called the opening angle

11

Bowtie Formulas


Characteristic impedance*


Z
C

= ln[cot(
θ
0
/4)]


Length*


L

= 0.5
λ
0
/(
ε
eff
)
1/2


Effective dielectric constant*


ε
eff

= 0.5(
ε
r
+ 1) + 0.5(
ε
r


1)(1 + 10
d
/
W
)
-
0.555


We plan to use FR
-
4 substrate


ε
r

~ 4.0
-
4.8 (decreases as frequency increases)


d

is typically 1.6 mm, but other thicknesses available

*Source: C. Guo and R. Liu. (2009, June). A 900MHz shielded bow
-
tie antenna system for ground
penetrating radar. [Online]. Available:
http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5550125&tag=1


12

Possible Design Options


Edge cutting can be used to increase bandwidth of
bowtie and decrease physical size

13


Another type of radiating element


14


Metal Patch antenna


Gain not very high


Not very robust

15

Design Challenges


How much gain can we get?


Feeding the antenna


Impedance matching


Determining spacing between PCB and backplate


Correctly interpreting simulation results


Simulation will require a lot of trial and error


16

Impedance Matching


Want to match impedances to minimize transmission
line reflections from antenna toward radio


Max Power Transfer


Low reflection coeff.


Low VSWR


This can be done both by changing antenna feed point
and by designing microstrip feedline impedance to be
Z
microstrip

= (Z
coax
Z
ant
)
1/2


17

Validation


Conduct impedance analysis using network analyzers
in Applied EM Waves Lab.


Time reserved for use of anechoic chamber at SEL


Use to make antenna pattern measurements


900
-
MHz feed & measurement system available
(antenna, signal generator, network analyzer, etc.)


Most of our measurements will be focused on figures
of merit, since SEL will have to have the antenna
characterized before production

18

Software


Agilent Advanced Design System (ADS) with
Electromagnetic Professional (EMPro)


SEL is planning to incorporate

ADS Design Suite for
future projects


FEM Simulator


FDTD Simulator


Method of Moments


Impedance Analysis




19

Progress


Currently a little behind according to our timeline


Issue with EMPro software


The software is unable to work correctly with standard
Intel Graphic Chipsets


Needed to order an Nvidia graphics card and install into
a laboratory computer


Works great now


In the future we will want to upgrade the RAM from
2GB to 4GB


20


Working on getting tutorials to learn the software


Need to wait for the University license instead of our
trial version to obtain access to the tutorials


Have put in our order for the University license

21

Budget


EMPro Software
-

$2000


Nvidia GT 430 Graphics Card
-

$85


Kingston
2
GB RAM
-

$25


N
-
Connectors
-

$4 Each


PC Board and metal back plate


Provided by SEL



22

Schedule

23

Questions?

24